The scouting toolkit

December 5, 2012 - Issue 33

The standard sweep net has a 15" (38 cm) diameter. Source: Shelley Barkley, AARD

Professional entomologists, plant pathologists and agronomists use many of these tools. Growers may want to keep some or all of them handy as well.

Smart phone

Various growers and agronomists who answered a Twitter query about scouting tools said their smart phone was a key tool for collaborating with others, keeping records, and taking photos. It can sometimes be difficult to identify an insect by photo alone. To help entomologists with insect identification by photo, include various angles of the insect (top, side, front), photos of the damage the insect is causing, and photos that show where the insect is feeding on the plant. Keep these four basic pieces of information for each photo: What crop is the insect in (and where on the plant was it found), location of the field (legal location or GPS if possible), name of the person who collected the sample or took the photo, and the date.

Seed depth tool

Growers can use the tool to make sure every run of the drill places canola at the recommended half inch to one inch depth. Click here for tips on where and how to check seed depth.

Hand trowel

Hand trowels are handy for wireworm and cutworm scouting, and trowels with depth markings on them can also be used to  determine the depth from which seedlings are emerging while evaluating health of hypocotyls and roots. When scouting for underground cutworms, look aboveground for bare patches, holes or notches in foliage, and clipped plants. Start digging where you find damaged or missing plants. In moist soils, cutworms will stay close to the surface. In dry soils, they may go down 8-10 cm (up to 4”). Dig up soil from a one square foot area to a depth of 10 cm and put it into a basin. Loosen the soil and shake it up to activate cutworms. Repeat a few times throughout the field. A sieve can help separate insects from dry soil. Find a sieve or strainer with holes big enough for your soil type.

Sweep net. Source AARD

Standard sweep net

Lygus bug and cabbage seedpod weevil economic thresholds are based on sweep net counts, and proper counts depend on using the standard sweep net and technique. The standard size has a 35” long handle and 15” (38 cm) diameter net. Lygus can show up in all areas of the Prairies, but even if you don’t typically have lygus or cabbage seedpod weevil, a sweep net can be useful to identify the presence of beneficial insects, of diamondback moth larvae and other insect pests. Alberta’s government site has info on where to buy them.

Large Ziploc bags, especially the breathable ones, are a handy companion for the sweep net. Flying insects can pop out of the net quickly, making it harder to do an accurate count. Carefully dump all contents into a Ziploc bag, then count insects through the perforated bag.

Note: Sweep net sampling is notoriously variable. Making a spray decision based on one set of 10 sweeps means a high chance of making the wrong decision. Extension entomologists recommend a minimum of 5 sampling sites, in a W or X pattern throughout the field, with 10 sweeps at each site. With lygus in particular, time of day, temperature and wind speed can make a difference in counts. You may want to scout two days in a row, unless average numbers are well above threshold.

Magnifying glass/hand lens

A 10X magnifying glass can be used to identify different insect species based on specific markings, to identify very small insects, such as thrips, to spot pycnidia in blackleg lesions, and to look at the growing points of frosted canola to see if they’re regrowing.

Three sided or two sided “square”

Some insect thresholds are based on counts per square foot or square metre, so use a two or three sided “square” to slip more easily into a heavy canopy and help you more accurately estimate the area of your counts. A home-made two-sided square, with a grid on each length showing one foot, half metre and full metre lengths will serve multiple purposes.  With open sides, the square slips into the canopy more easily than a full square. For bertha armyworm, for example, lay down the square with the half metre length on each side, give canola plants a shake and count the berthas that fall into that half metre by half metre square. Multiply by four to get the count per square metre.

Hoop or metre stick

Plant counts can help you assess whether the stand has reached the minimum 40-50 per square metre, and whether these stands are uniform throughout the field. This can help with reseeding decisions and seeding rate assessment, and in future decisions about pest threats and whether thresholds should be lowered if plant stands are at critical low levels. Click here for more on how to do counts with a metre stick or hoop.

Clippers for cutting stems to check for blackleg.

Clippers

To check fields for incidence and severity of blackleg, you want to clip stems just before swathing and look at their cross sections. Click here for tips and a how-to-clip video. Clippers provide a nice clean cross section, better than a jack-knife. Splitting stems by hand is too difficult and destructive to provide a good cross section. Spend the money on a good set that can cut through a large canola stem cleanly. Buy stainless steel (avoid carbon steel) so they can be disinfected and will not rust.

This is an elaborate insect collector's kit with numerous small vials and an aspirator.

Containers for insect samples

Growers and agronomists scouting fields are often the first line of defense when it comes to identifying first arrivals each year and identifying new insect pests. But this defense is useless if the insect can’t be identified. Vials or sturdy plastic containers will keep insects in good shape while in transport to the lab. Ziploc bags with perforations work really well for grasshoppers. Paper bags work for keeping samples of stems covered with aphids.

Aspirators can help suck insect specimens off a plant and put them into the vials. An aspirator plugs into the top of the vial, and has hoses going in and out. You suck on one end and hold the other end up to insect, vacuuming them up the hose and into the vial. This is faster than tweezers and does less damage to the insect making identification easier.

Booties to prevent spread of soil on boots.

Booties

Biosecurity is important for anyone moving from field to field and farm to farm. Mud on the bottom of boots can spread noxious weed seeds and clubroot spores. The amount of soil required to initiate clubroot infection in a new field is unknown. Therefore, any soil transfer from an infested field should be viewed as a risk. Growers and agronomists and anyone else who walks fields is encouraged to use disposable booties, especially if they’re in a known or suspected clubroot region. Use one set of booties per field, and dispose of used ones properly. If rubber boots are worn without booties, they will need to be scraped clean, washed (washing can be done in a 20L pail or a Rubbermaid type container with lid) and disinfected before the next visit. Include a spray bottle of sterilizer for cleaning boots and equipment between fields and garbage bags for disposal of booties or to wrap contaminated equipment. Click here and read “Recommended Guidelines for Field Entry Activities.”

Flags

If you find an area with suspicious weeds, disease lesions, or building insect populations, it can be helpful to mark them so you can come back to that same spot and monitor the potential problem. Plastic stemmed flags are preferred in case you forget them in the field and accidentally cut them with the swather.

Gloves

Nitrile or latex gloves should be part of your biosecurity kit, and can keep your hands clean when handling insects, plant roots, etc.

Beating sheet

This is an expandable white sheet made from plasticized material. It has cross pieces underneath to keep corners square. Entomologists often have these on hand for field days, to bang out aphids, caterpillars or other insects to do accurate counts. For growers, the hood of the truck or tail gate is often handier and can be just as effective.

Resource material

Keep Canola Council of Canada factsheets, disease publications and crop disease pictures as resources for identification of disease, pests and deficiencies.

Notebook

A notebook and pen, either the real thing or an electronic version, is handy to record details of areas to return to for monitoring, noting distribution of disease, sampling, etc. Also have a grease pencil or Sharpie on hand to mark containers.

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